diff --git a/apps/dsm/mods/mod_utils/ModUtils.cpp b/apps/dsm/mods/mod_utils/ModUtils.cpp
index 13c043e8..86e044e0 100644
--- a/apps/dsm/mods/mod_utils/ModUtils.cpp
+++ b/apps/dsm/mods/mod_utils/ModUtils.cpp
@@ -872,4 +872,4 @@ EXEC_ACTION_START(SCDecryptCodeAes128CBC) {
   /* unbase64() uses malloc, don't forget to free() */
   free(encryptedCodeRaw);
 
-} EXEC_ACTION_END;
\ No newline at end of file
+} EXEC_ACTION_END;
diff --git a/core/AmB2BSession.h b/core/AmB2BSession.h
index 542193c9..ffb85fea 100644
--- a/core/AmB2BSession.h
+++ b/core/AmB2BSession.h
@@ -95,7 +95,7 @@ struct B2BSipReplyEvent: public B2BSipEvent
   string sender_ltag;
 
  B2BSipReplyEvent(const AmSipReply& reply, bool forward,
-		  string trans_method, string sender_ltag)
+		  const string& trans_method, const string& sender_ltag)
    : B2BSipEvent(B2BSipReply,forward),
     reply(reply), trans_method(trans_method), sender_ltag(sender_ltag)
   { }
diff --git a/core/AmConferenceChannel.cpp b/core/AmConferenceChannel.cpp
index 3b2f86a5..a53c184e 100644
--- a/core/AmConferenceChannel.cpp
+++ b/core/AmConferenceChannel.cpp
@@ -5,9 +5,17 @@
 #include <fstream>
 #include <string.h>
 
-AmConferenceChannel::AmConferenceChannel(AmConferenceStatus* status, int channel_id, string channel_tag, bool own_channel)
-  : status(status), channel_id(channel_id), channel_tag(channel_tag), own_channel(own_channel),
-    have_in_sr(false), have_out_sr(false), in_file(NULL), out_file(NULL)
+AmConferenceChannel::AmConferenceChannel(AmConferenceStatus* status, int channel_id,
+    const string& channel_tag, bool own_channel)
+  :
+    own_channel(own_channel),
+    channel_id(channel_id),
+    channel_tag(channel_tag),
+    status(status),
+    have_in_sr(false),
+    have_out_sr(false),
+    in_file(NULL),
+    out_file(NULL)
 {
   assert(status);
   conf_id = status->getConfID();
diff --git a/core/AmConferenceChannel.h b/core/AmConferenceChannel.h
index 501600e4..e4415fea 100644
--- a/core/AmConferenceChannel.h
+++ b/core/AmConferenceChannel.h
@@ -81,7 +81,7 @@ class AmConferenceChannel: public AmAudio
 
  public:
   AmConferenceChannel(AmConferenceStatus* status,
-		      int channel_id, string channel_tag, bool own_channel);
+		      int channel_id, const string& channel_tag, bool own_channel);
 
   ~AmConferenceChannel();
 
diff --git a/core/AmEventDispatcher.h b/core/AmEventDispatcher.h
index c0757bb8..e2c650c4 100644
--- a/core/AmEventDispatcher.h
+++ b/core/AmEventDispatcher.h
@@ -48,7 +48,7 @@ public:
       QueueEntry(AmEventQueueInterface* q)
         : q(q), id() {} 
 
-      QueueEntry(AmEventQueueInterface* q, string id)
+      QueueEntry(AmEventQueueInterface* q, const string& id)
 	: q(q), id(id){} 
     };
 
diff --git a/core/AmSdp.cpp b/core/AmSdp.cpp
index 59d5c6dd..0bd475aa 100644
--- a/core/AmSdp.cpp
+++ b/core/AmSdp.cpp
@@ -52,8 +52,8 @@ static char* parse_until(char* s, char* end, char c);
 static bool contains(char* s, char* next_line, char c);
 static bool is_wsp(char s);
 
-static MediaType media_type(std::string media);
-static TransProt transport_type(std::string transport);
+static MediaType media_type(const std::string& media);
+static TransProt transport_type(const std::string& transport);
 static bool attr_check(std::string attr);
 
 enum parse_st {SDP_DESCR, SDP_MEDIA};
@@ -858,7 +858,7 @@ static void parse_sdp_media(AmSdp* sdp_msg, char* s)
         if (next > media_line)
           media = string(media_line, int(next-media_line) - 1);
 
-        m.type = media_type(std::move(media));
+        m.type = media_type(media);
 
         if (m.type == MT_NONE) {
           ERROR("parse_sdp_media: Unknown media type\n");
@@ -1501,7 +1501,7 @@ inline char* skip_till_next_line(char* s, size_t& line_len)
 /*
  *Check if known media type is used
  */
-static MediaType media_type(std::string media)
+static MediaType media_type(const std::string& media)
 {
   if(media == "audio")
     return MT_AUDIO;
@@ -1519,7 +1519,7 @@ static MediaType media_type(std::string media)
     return MT_NONE;
 }
 
-static TransProt transport_type(string transport)
+static TransProt transport_type(const string& transport)
 {
   string transport_uc = transport;
   std::transform(transport_uc.begin(), transport_uc.end(), transport_uc.begin(), toupper);
diff --git a/core/AmSession.h b/core/AmSession.h
index 5e90a19e..9abfd00e 100644
--- a/core/AmSession.h
+++ b/core/AmSession.h
@@ -203,7 +203,7 @@ public:
     int code;
     string reason;
     string hdrs;
-    Exception(int c, string r, string h="") : code(c), reason(r), hdrs(h) {}
+    Exception(int c, const string& r, const string& h="") : code(c), reason(r), hdrs(h) {}
   };
 
   /**